Nuclear waste is the by-product of reactors that turn out plutonium and other nuclear materials. The problem of storing nuclear waste has built up over the last three decades and continues to get worse. It has been reported that nuclear waste is increasing at a current rate of about 1.5 million gallons a year and it has been estimated that at the end of 1980, 76.8 million gallons were stored by the Department of Energy. It has also been reported that the Department of Energy is running out of space for new tanks for storing nuclear waste and that some of the older tanks have developed leaks.
Concerted efforts are being made to find safe techniques and facilities for processing and storing such waste. For example, it has been proposed to compress the volume of such waste by combining waste now sitting in tanks in the form of brown sludge with a special form of glass. The glass-like mixture is then sealed in stainless steel cylinders which are stored in permanent underground storage sites. By combining the sludge with glass, the volume of waste is sharply reduced and solidified in a permanent form.
The design and construction of facilities for storing and/or processing nuclear waste requires the solution of numerous problems relating to safety before the construction of such facilities can be deemed to be feasible. For example, the buildings for such facilities must be constructed to withstand earthquakes as well as other seismic disturbances. The area in which the nuclear waste is handled, sometimes referred to as the "hot canyon" area, for all practical purposes cannot be entered by operating personnel. These considerations place severe design limitations on equipment, particularly cranes, which must be used in such facilities.
The requirement that such buildings have seismic integrity places a premium on space and, accordingly, the height and width of overhead cranes for use in such facilities are severely limited. Because the level of radiation for operating personnel is too intense in the hot canyon area to permit entry, such cranes muct be designed to operate by remote control. Multiple levels of redundancy are required in the design of such cranes to insure that in the event of breakdown, the crane can be removed from the hot canyon area.
The on-board crane control mechanisms, e.g., motion control systems, radio control systems, closed circuit television camera control systems, etc., are the most vulnerable parts of the crane with respect to potential breakdown. Such control mechanisms must be shielded from direct exposure to the relatively intense levels of radiation in the hot canyon area to insure reliable performance. Typical low cost barrier materials, such as concrete, add large amounts of weight to the crane in addition to taking up valuable space. It is necessary to store the on-board control mechanisms in a manner so as to limit their exposure to radiation and to permit access to such controls and at the same time not burden the crane with undue weight and lost space.